Turret construction



Feb. 1, 19441. MARls 2,340,334

TURRET CONSTRUCTION Filed July 10, 1941 2 sheetskshget 1 & i

as as 7 4- lwswran flarzyB Mar/ls Patented Feb. 1, 1944 UNITED- STATE Si PATEN T OFFICE runner ooNs'rRUo'rIoN Harry B: Maris, Riverdale Application July 10, 1941,.Ser ialNof4 0 1J5 1 9 Claims, (Child-8 (Granted under the act of- March. 3, .1883, as amended April 30, 1928; 370 0. G. 757) invention relates to improvements in turret construction and more particularly to such improvements involving the rollers and ute arias? Roller paths ground asfaccuratelyas pos' sibleto. plane. surfaces were formed on the portion o'fithe turret which rested on the rollers. and o'nithe portion of thefoundation upon which the rollers rested The portions ofthe structure upon which thes'e roller paths were ground fitted snug- 13', down upon the roller faces between the roller flanges. Lateral movement of the turret with re spect'to its foundation resulting from th recoil o f theturret guns 'or th explosions of enemy projectiles, in proximity to the turret was resisted by the roller flanges. In order to prevent vertical movement of the turret relative to its foundation due to the recoil action orthe explosion of pro- .ieotiles, holding down clips were formed on the turret structure.

extended beneath an overhanging portion of the foundation structure normally clearing it by a small amount.

The use of large flanged solid rollers presented several disadvantages. It necessitated the employment. of large and heavy foundations in the turret structures upon which roller paths could be, ground. The use of holding down clips required a large clearance, space between the barbet te and. the portion of the turret structure which revolved inside it. The large size of the rollers employed introduced a large factor of torque intothe recoilaction since the diameter of the rollers introduced a large vertical displacement between the roller paths. Furthermore, the m ash ning of wide roller paths such as required by thisstruoture is a task very difficult of accomplishment. Qn' the other hand the presence of any irregularities in the turret paths caused the entire weightof the turret structure to be sup- PKFFQPY 3 3. 4.5 1 3 umber 9 3 W Fh the result that rollers must be of such size that the entire weight of the turret could be borne by a I These were in the shape of. brackets which projected from the turret and few of them. Moreover, roller path irregufretting abrasion.

dation These'g ears regardless of their large size must be protected from recoil stresses and could 91 b s d normal mine. r t n f g nfi The driving mve hei mwes he or placed s near the plane of fire as possible'so that the recoil would tendto separate the'gear from the rack.

Another disadvantage attending the use of large flanged rollers was the inability to prevent the anger dirt and foreignfmatter between the b'e'aringsurfaces since it was impossible to adequately house theroller asse nbly, It was necessaryto protct'thespiir training gear from the whip "due to' the fi'ring of the singlewing gun I and from ShOOk I eS'l lmiflglIfQlfll. the-impact Of an enemy projectile, by a release in the driving m'otorQ M I Turret installationsaboard ship are subject to longperio'ds of non-use with'the turret maintained at a fixed ang ed train. Durin these periods the'm'otio'n of the ship subjects the rollers and the roller pathslto constant weardueto the srnall vibratoryvertioalmovements of the turretrelativetojts foundation.- This wear is called it is object of turret construetionwhich'will result in a great saving of weight overthose previously used. It is a further object of this invention to providea t'urr'et construction which will "considerably reduce the necessary clearance between the rotating parts of the turret and the barbette. It is a still further object off'thisinvention to provide a turret construction utilizing hollow fiexible rolle'rs capabl'eof yielding teasers distribution of the turret weight when irregularities are encountered in the roller path clearances. It is also an object of this invention to provide a turret construction utilizingj'a series of horizon a11ydi's: p'psed hollow rdllers and a series of vertically disposed hollow rollrs for the'purpose of absorbinghorizontal fdrces without the development of torque. It is another object of this invention to provide a turrt'construction utilizing flexible rollers which will vield uponthe application of sev restrsstoauow' solid contact between the rotating the thffiiieu portions or the turret structure for transmission 'of said forces from the rotating to thefixed structure; It is another biei "it i nie l fi i f d a l e and this invention to provide a roller path assembly which will allow the rollers to be completely enclosed and thus effectively guard the assembly against the intrusion of dirt and foreign matter and allow it to be effectively lubricated. It is another object of this invention to provide a training system which will be much more rugged than the type using the spur gear and will be capable of absorbing the shock of recoil whip or of projectile impact without the necessity of a release mechanism. It is another object of this invention to provide a means for protecting the rollers from fretting abrasion. Other objects will become apparent from a consideration of the following description taken together with the accompanying drawing in which:

Fig. 1 is a plan view of the pan floor of a turret showing the top of the roller and roller path assembly and having a portion cut away to show a portion of the training rack;

Fig. 2 is a plan view of a fragment of a turret wall showing the worm gear arrangement for training the turret;

Fig. 3 is an elevational view of one of the worm gears used to drive the turret together with the details of its bearing system;

Fig. 4 is an elevational view in section of a fragment of the turret taken along the line 4-4 of Fig. 3; I

Fig. 5 is a side elevational view in section of a portion of the turret wall and turret foundation wall showing the arrangement of the roller path, rollers and holding down means;

Fig. 6 is a side elevational view of a section of the turret and foundation walls extending around the turret from the sectional view of Fig.

Fig. 7 is a plan view in section of a portion of the structure shown in Fig. 6 taken along line 11 of that figure, and r Fig. 8 is an elevational view in section of a modified form of roller path and roller assembly.

The details of-one embodiment of the invention may best be seen in Fig. 5 where there is shown a turret wall I positioned in coaxial relationship to, and outside of, a cylindrical turret foundation 2 with the lower end of the turret wall extending downwardly past the upper end of the turret foundation and having a slight clearance with respect thereto. inner side of the turret wall I is anupper path ring 3 having formed on its lower face a surface 4 ground as accurately as possible to a true plane. The upper end face 5 of the turret foundation 2 is likewise ground to aplane surface parallel to 4. Between these surfaces is positioned a series of hollow steel rollers 6. Welded to'the inner face of the upper path ring 3 is a cylindrical side wall I extending'downwardly from the ring 3 and spaced from the foundation 2 by only a small clearance. Machined in the upper end of the inner face of foundation 2 is an annular recess having a vertical wall 8 ground as accurately as possible to a true cylindrical surface. Opposite to this recess is formed a cooperating annular recess having a vertical wall 9 ground to a true cylindrical surface. Taken together these two recesses form a single annular recess of rectangular cross-section. Positioned in this recess is a series of rollers I0 which are similar in construction to the rollers 6. Also ground in the opposing faces of the foundation 2 and the side wall I is a key way in which floats a key I I. -Welded to the inner surface of thefoundation wall 2 is a-ring I2 of rectangular cross-section having its upper sur- Welded to the normally occupies when not in use.

face accurately ground to a plane. The lower end of the side wall I is ground to a conical surface I3 sloping upwardly and out. Welded to the inside of the side wall 1 with its upper surface level with the bottom of the rollers III is the pan plate M. As best shown by Fig. 6 there are provided in the wall 'I a pair of removable sections I5 of which only one is shown in Fig. 6. These are bolted to the ring 3 by means of lag bolts I6 and by their removal the rollers 6 and I0 may be inserted in their respective places. There is likewise provided in wall I a pair of removable sections I! of which only one is shown in Fig.6. These sections are normally held in place by upwardly directed lag bolts I8 which attach the sections to the wall "I. These removable sections are spaced apart.

Between the lower end face I3 of the wall I and the upper face of ring I2 are positioned a series of locking blocks I9 as shown in Fig. 6. These blocks are for the purpose of removing the weight of the turret from the horizontal.

rollers. 6 when the turret is not in use. The number and, lengths of these blocks, are such that their combined length would be somewhat. less than half the circumference of the wall 1."

As shown in Fig. 6 a series of slots 20, each slightly longer than oneof the blocks I9 and spaced apart by the same distance, are cut in the conical surface I3 of the wall I for the admission of the blocks I9. Where these slots are cut the lower end of wall 1 extends horizontally rather than at an angle with the horizontal as shown in Fig. 5. At the left hand end of each of these slots as shown in Fig. 6 a downwardly extending lug 2I having a radially directed right hand face is welded to the surface I3. Located opposite the lug 2| is a lug 22 of similar configuration welded to the upper surface 23 of ring I2. Also welded.

to the surface 23 at the right hand end of the slot20 as shown in Fig. 6 is a lug 24 having a vertical side 25 which slopes as shown in Fig. 7. The right hand end of block I9 has the same slope, as shown in Fig. '7. The blocks I9 have a cross-sectional shape similar to that of the space between the surface I3 and 23, as shown in Fig. 5. V v

The operation of the blocks I9 to lock the turret from movement while it isnot in use is as follows:.

Theblocks are assembled in the portions of the space. between surfaces I3 and-23 provided with the slots 20, with the turret turned in a clockwise direction from the position of rest'it The extent of this movement is such that each of the lugs 2| will have traveled in a clockwise direction thelength of one of the slots 20. The relationship between the wall 7 and the ring I2 will now be that shown in Fig. 6. With the blocks I 9 in place the turret is now trained in a counterclockwise direction until it occupies its normal position of rest. When in this position the lugs 2| will have moved in a counter-clockwise direction an amount such that each block I9 will no longer liewithin a slot 20 but will have been positioned entirely beneath one of the unslotted sections of I3. When in this position the blocksi9 prevent any vertical movement of wall 1 with respect to foundation. In order to release the blocks I9 from their locking position the turret is now trained in a clockwise direction until the wall 1 and the ring I2 again occupy the positions shown in Fig. 6. Now any further movement of the turret in a clockwise direction will cause assessethe surfaces-ii; o "th mast-A t r: is therb ocksl 9- 'fromtheir-places :andthey will tall clear; for" ist could then beplaced on. the upper face 23 of ring I2. The faces on the inner side of turret wall'l, the lower surface 40f ring 3 andthe outer surface of' wall I would then. be ground. Thegrinding completed, the turret would now be lifted on jacks, the collar resting on ring l2' removed and the turret wouldbe lowered on to its'support on rollers 6 which would be rolled into place between ring 3 and foundation wall 2 through the removable sections l5; When all the. rollers were in place and carrying the weightof the turret the rollers H3 could be rolled into t-heirseat by-rotation of the turret while they: are being inserted through the removable section 15. The key H is in sections of such a lengththat .theymay beinserted by removal of sections ll. A sample section of the key should be machined to a free sliding clearance around the entire circle of its groove. Withthis segment as a pattern the other segments should be machined to the same dimensions and then inserted through the opening left by removal of section ll".

Figs. 1, 2, 3 and 4 show the improvements in the training mechanism contemplated by the invention. The training rack is shrunk on the outside of a downwardly extending annular member 3'I'welded' to the bottom of the pan plate M. While immovable with respect to member 31 under ordinary stresses, the rack 30 will slipunder the application of unusually heavy. stresses be-.

fore the other componentsof'the training gear will be harmed. Meshing with the rack 30' are a pair of worms 32 driven through pinions 33secured on the worm shafts. Motor 34; through ashaft 35 and spiral gears 36 and- 31; drives shaft 38 on the ends of which are secured gears 39' meshing with pinions 33. As shown in Fig. 2

the single motor 34 drives a pair ofworms 32.

A similar installation will be placed on the opposite side of thestructure. An installation of this type may be provided with worms each having sufficient strength to take a shock load of 500,000 pounds, which will be sufficient to absorb all shocks. resulting from firing or the explosion of an enemyprojectile against the outside of the turret, without the necessity of provision of a release means. In ship installations the motors could be placed along the fore and aft center line of the ship. Suchpositioning of spur gears is impossible due to thenecessity of keeping the spur gear out of a position normal to the line of fire. Nor can a spur gear installation be so positioned that the driving mechanism is carried by the turret stool, since, if so-carried', the spur gear could not be separated from the rack upon recoil, for all angles of'fire.

Fig. 8 shows a modification. of theroller path assembly such as illustrated in Fig. 5. In the event that longer and larger rollersthan the roller 6 shown in Fig. 5 are required, the-.n'iodiflcation shown in Fig. 8. is preferred. In thismodifica-- rack has been mounted on the turretstool.

, 44-. welded to ring 43.

tioni the-dimensions; of theroller fixhave beeneinecreased andu the roller hasbeendivided intoth're'e sections. 'FI'hisismadetnecessary by the. necessity-.1, of'tapering -a roller- 0f this length for frictionless rollingcon a circular track.- Withthe long roller. provision of the required taper-is not practicable. Straight rollers maybeused in short lengths.

With therollerso dividedeach section rotates; at a slightly differentiateandthe difierentsections wouldineed to be kept in line by a tapered guide which is-notshown. The numbers and. functions of most of the parts in this-figure are. the same as those in Fig.- v5. However, in order to increase the width ofthe lower, roller path the, plate 40 has been welded to the upper-portion of the inside of the inside offoundation 2. The pan plate 1.4 is welded directly. to the inner-surface of thisplate and the rollers [0 rest on top of'the pan plate, the. slot for their accommodation being formed entirely in wall I. The wall- I has thus been split into 2 rings the lowermost of which is seen below the pan plate l4, being Welded toplate M. The. blocks I9 are employed as before. In-this case, however, the training The rack is indicated at M; Its upper surface is bevelledin the shape of a cone extending upwardlyand out. It is supported on a ring- 43 Welded to the turretfoundation above which is a plate In assembling the training 1 rack the base support 43 is first welded-in place with sufficientclearance to allow. the difierent sections of the training rackto be seated against plate 40, the bottom face ofwhich is bevelledto match the upper surface ofrack 4|. The key" plate 44 is then forced intoplace under high pressure, securely lockingthe training-rack in position. After 44 is seated, it is welded to 43, thus insuring-a permanent lock for the training rack, which however can be made to rotate under the application of heavy stresses.

The hollow rollers shown in the various embodiments should have a wallthickness approxi-. mately 1 0- thediameter of the roller. With *1- such a thicknessthe roller will be as strong as a solid roller of the same length and diameter. However, solid rollers of' the same length and. diameter could notbe used since the inherent inaccuracies in the roller paths plus those induced by irregular temperature distribution and movement of the ship in a seaway would produce irregularities in roller path clearancev which would result in injury either to the rollersor the roller path or both. However, by the use of flexible rollers which yield under stress the distribution of the load of the turret and of the forces of recoil is such as to reduce the stress on any one part of the structure and thus to avoidinjury to it.

Utilization of the invention should save weight in the order of tons perturret with the em,- bodiment shown in Fig. 5. In spite of this decrease in weight the assembly would be stronger because of its compactness and flexibility. Upon the application to the rollers of stresses of the magnitude of' those due to recoil, theywill' yield suifi'ciently to allow solid contact be to the stationary, parts ofrthe turretand thence to the structure of the ship or Other mounting platform. Horizontally acting stresses will be resisted by the contact of turret wall I with turret foundation 2 and also at the opposite side of the turret by the contact of wall 1 with the turret foundation 2.

The structure according to the invention presents a smooth exterior rotating surface having no projections which might be fouled by battle damage. This is a distinct advantage over the construction previously used. Because of the considerable decrease in interference between the rotating turret and the barbette due to the elimination of holding down clips, the diameter of the barbette could be materially reduced while "maintaining sufficient clearance. This would allow the saving of a strip of barbette armor of considerable length. If advantage is taken of this feature a total saving in weight in large 3-gun turrets could be as high as 200 tons per turret.

The use of small rollers and simple cross sections for the roller paths offers a possibility of the use of material of higher quality and the employment of better heat treatment. The shape of the various paths and parts of the assembly is such that rolled welded strips can be advantageously employed, with the greater uniformity and greater tensile strength which is available in such shapes over that obtainable with previously used forms of construction. The entire assembly can be packed in grease, thus giving better protection from dirt and moisture and better lubrication than can be obtained with an open bearing structure such as that necessary when flanged rollers are employed. The most important advantage resulting from the invention is the elimination of torque from horizontal thrusts communicated from the pan plate to the turret foundation.

It should be understood that the practice of the invention is not limited to the embodiments illustrated and described but only by the scope and limitations of the appended claims.

The invention described herein may be manufactured and/or used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A gun turret having a cylindrical turret wall and fixed cylindrical foundation'wall coaxial therewith and extending upwardly inside the lower end thereof, said foundation wall having a plane, horizontally extending, upwardly facing surface formed on its upper end, a ringshaped member secured to the inside of said turret wall and lying above said surface, said member having a similar but downwardly facing surface formed thereon, a series of horizontally extending flexible hollow rollers positioned between said surfaces, a cylindrical wall extending downwardly from said member inside, coaxial with said foundation wall and having a small clearance with respect thereto, said foundation wall and said cylindrical wall having annular recesses formed therein which cooperate to form a raceway of rectangular crosssection having vertical side walls accurately formed to cylindrical shape, a series of vertically disposed hollow flexible rollers positioned in said raceway and under normal conditions maintaining a clearance between said cylindrical wall and said foundation wall, said cylindrical wall and said foundation wall having a key way formed 'thereb'etween, a key in said key wayan'd a pan plate secured to said cylindrical wall with its upper surface lying in substantially thesame plane as the lower ends of saidvertically disposed rollers.

2. A gun turret having a cylindrical turret wall and fixed cylindrical foundation wall coaxial therewith and extending upwardly inside the lower end thereof, said foundation wall having a plane, horizontally extending, upwardly facing surface formed on its upper end, a ringshaped member secured to the inside of said turret wall and lying above said surface, said member having a similar but downwardly facing surface formed thereon, a series of horizontally extending flexible Hollow rollers positioned between said surfaces, a cylindrical wall extending downwardly from said member inside, coaxial with said foundation wall and having a small clearance with respect thereto, said foundation wall and said cylindrical wall having annular recesses formed therein which cooperate to form a raceway of rectangular crosssection having vertical side walls accurately formed to cylindrical shape, a series of vertically hollow flexible rollers positioned in said raceway and under normal conditions maintaining a clearance between said cylindrical wall and said foundation wall, said cylindrical wall and said foundation wall having a key way formed therebetween, and a key in said key way.

3. A gun turret having a cylindrical turret wall and fixed cylindrical foundation wall coaxial therewith and extending upwardly inside the lower end thereof, said foundation wall having a plane, horizontally extending, upwardly facing surface formed on its upper 'end, a ring shaped member secured to the inside of said turret wall and lying above said surface, said member having a similar but downwardly facing surface formed thereon, a series of horizontally extending flexible hollow rollers positioned between said surfaces, a cylindrical wall extending downwardly from said member inside, coaxial with said foundation wall and having a small clearance with respect thereto, said foundation wall and said cylindrical wall having annular recesses formed therein which cooperate to form a raceway of rectangular crosssection having vertical side walls accurately formed to cylindrical shape, and a series of vertically disposed hollow flexible rollers positioned in said raceway and under normal conditions maintaining a clearance between said cylindrical wall and said foundation wall.

4. A gun turret having a rotating portion and a foundation portion, said rotating portion including a cylindrical side wall and a circular pan plate fixed to the inside of said cylindrical side wall to rigidly maintain the cylindrical contour of said side wall, said foundation por tion being unsupported radially in the plane of the pan plate, a series of horizontally disposed rollers positioned between superimposed horizontally extending surfaces of said portions and normally bearing the weight of said rotating portion, a series of vertically disposed rollers positioned between opposing vertically extending cylindrical surfaces formed on said portions with their bases in a plane substantially aligning with the upper surface of said pan plate and establishing and normally maintaining a fixed small clearance between vertically extending surfaces of said rigid side wall and said foundation portion, said rollersbeingso compressible .as ther formed'to provide a'seco'nd seriesjof spaced to yield upon the application to said rotating portion of stresses in a direction normalto their respective roller paths, thereby temporarily removing the clearances-established and normally maintained by said rollers and allowing contact between opposing surfaces of said portions which extend in directions parallel to their respective roller paths.

5. In a gun turret having a rotating portion, a foundation portion and a series of horizontally disposed rollers positioned between horizontally extending surfaces of said portions and normally bearing the weight of said rotating portion; means for locking said rotating portion against vertical or horizontal movement relative to said foundation portion while said rotating portion is not in use, said means comprising a series of blocks, said portions having opposing surfaces each formed with a series of recesses in matching locations, whereby, for a particular angle of train, a series of spacedapart chambers are formed between said surfaces wherein said blocks may be loosely positioned, said surfaces between said chambers being spaced apart to snugly fit said blocks, the end walls of said recesses and the ends of said blocks being so formed that upon training said rotating portion in one direction from said angle of train said blocks will become tightly held between said surfaces and will hold said rotating portion against vertical or horizontal movement with respect to said foundation portion and said blocks will be injected from said recesses upon rotation of said rotating portion in the opposite direction from said angle of train.

6. In a gun turret having a rotating portion, a foundation portion and a series of horizontally disposed rollers positioned between horizontally extending surfaces of said portions and normally bearing the weight of said rotating portion; means for locking said rotating portion against vertical or horizontal movement relative to said foundation portion while said rotating portion is not in use, said means comprising a series of blocks, said portions having opposing surfaces so shaped that, for a particular angle of train, a series of spaced-apart recesses are formed wherein said blocks may be loosely positioned, and a plurality of lugs formed upon said opposing surfaces, said lugs being so shaped and so positioned as to force said blocks into tightly fitting relationship between said surfaces upon movement of said rotating portion in one direction from said angle of train and to eject said blocks from said recesses upon rotation of said rotating portion in the opposite direction from said angle of train.

'7. In a gun turret having a rotating portion, a fixed foundation, and a series of horizontally disposed rollers positioned between horizontally extending surfaces of said rotating portion and said foundation, and normally bearing the weight of said rotating portion; means for locking said rotating portion against vertical movement relative to said foundation while said rotating portion is not in use, said means comprising a series of blocks, a shelf formed on said foundation upon which said blocks may be positioned, said rotating portion having downwardly facing surfaces formed thereon and lying above said shelf, said surfaces being formed to provide a first series of recesses between it and said shelf, each of which will loosely accommodate one of said blocks, said surface being furrecesses alternating those of said first seriesand each of such sizethatione of said blocks'may 'be' tightly held therein'whereby'vertical or horizontal movement of said rotating portion relative to said foundation "will be prevented, "a first series of dependinglugs having radially extending lateral faces formed on said surfaces and each positioned adjacent one end of one of said first series of recesses, each of said lugs occupying a similar position with respect to its recess, a second series of similarly shaped upwardly directed lugs formed on the upper surface of said shelf and so located that each may lie directly under one of said dependent lugs and a third series of upwardly directed lugs, the lugs of said third series being formed on said shelf and each being positioned at the opposite end of one of said first series of recesses from said previously mentioned lugs, each of said third series having an inclined vertical face, whereby when the lugs of said first series lie directly above those of said second series and said blocks are positioned in said first series of recesses, movement of said rotating portion in one direction will cause said first series of lugs to move said blocks into said second series of recesses, whereas under the same conditions movement of said rotating portion in the opposite direction will cause the lugs of said third series to eject said blocks from their positions between said shelf and said downwardly facing surface formed on said rotating portion.

8. A gun turret having a rotating portion and a foundation portion, said rotating portion comprising a cylindrical side wall and said foundation portion comprising a cylindrical wall surrounding a portion of said rotating side wall and being radially unsupported in the region where such overlap occurs, a horizontally extending annular roller path formed on each of said portions and lying above and outside the facing surfaces of said rotating side wall and said wall, a series of compressible rollers positioned between said roller paths and normally bearing the weight of said rotating portion, a cylindrical roller path formed on each of said facing surfaces, a series of compressible rollers positioned between said cylindrical roller paths, said portions being formed with horizontally extending superimposed surfaces, said surfaces and portions of said facing surfaces being normally held from contact by a very small clearance by said rollers, the compressibility of said rollers being such that upon the action of any abnormal thrust such as those encountered upon recoil of the guns carried by said turret said rollers will yield sufficiently to allow said surfaces to come into contact and thus communicate the stresses directly from said rotating portion to said foundation portion through direct contact of said portions, said cylindrical wall yielding in its radially unsupported region to allow such direct contact over a large area thereof.

9. In a device of the class described, a fixed cylindrical base member, a movable cylindrical member, means for supporting the movable member against shock and for concentric rotation relative to the fixed member, one of said members being disposed at least partially within the other, an annular ring having a prestressed fit over the outside of the inner member and disposed in the vicinity of the supporting means, said annular ring being of small cross-sectional area relative to its circumference and of resilient material, power drive means for rotating the annular ring relative to the fixed member including means automatically locking the annular ring in any position relative to the fixed member, whereby any shock imparted to said movable member tending to either start or stop rotational or translational movement thereof will be cushioned by circumferential stretching and local slippage of the annular ring relative to the inner cylindrical member thus making the annular ring an integral part of the shock supporting system.

HARRY B. MARIS. 

